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// Copyright 2008 Google Inc.
// Author: Lincoln Smith
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// VCDiffCodeTableReader is a class to interpret a stream of opcodes
// as VCDIFF instruction types, based on a VCDiffCodeTableData structure.
#include <config.h>
#include "decodetable.h"
#include "codetable.h"
#include "logging.h"
#include "varint_bigendian.h"
#include "vcdiff_defs.h"
namespace open_vcdiff {
VCDiffCodeTableReader::VCDiffCodeTableReader()
: code_table_data_(&VCDiffCodeTableData::kDefaultCodeTableData),
non_default_code_table_data_(NULL),
instructions_and_sizes_(NULL),
instructions_and_sizes_end_(NULL),
last_instruction_start_(NULL),
pending_second_instruction_(kNoOpcode),
last_pending_second_instruction_(kNoOpcode) {
}
bool VCDiffCodeTableReader::UseCodeTable(
const VCDiffCodeTableData& code_table_data, unsigned char max_mode) {
if (!code_table_data.Validate(max_mode)) return false;
if (!non_default_code_table_data_.get()) {
non_default_code_table_data_.reset(new VCDiffCodeTableData);
}
*non_default_code_table_data_ = code_table_data;
code_table_data_ = non_default_code_table_data_.get();
return true;
}
VCDiffInstructionType VCDiffCodeTableReader::GetNextInstruction(
int32_t* size,
unsigned char* mode) {
if (!instructions_and_sizes_) {
VCD_ERROR << "Internal error: GetNextInstruction() called before Init()"
<< VCD_ENDL;
return VCD_INSTRUCTION_ERROR;
}
last_instruction_start_ = *instructions_and_sizes_;
last_pending_second_instruction_ = pending_second_instruction_;
unsigned char opcode = 0;
unsigned char instruction_type = VCD_NOOP;
int32_t instruction_size = 0;
unsigned char instruction_mode = 0;
do {
if (pending_second_instruction_ != kNoOpcode) {
// There is a second instruction left over
// from the most recently processed opcode.
opcode = static_cast<unsigned char>(pending_second_instruction_);
pending_second_instruction_ = kNoOpcode;
instruction_type = code_table_data_->inst2[opcode];
instruction_size = code_table_data_->size2[opcode];
instruction_mode = code_table_data_->mode2[opcode];
break;
}
if (*instructions_and_sizes_ >= instructions_and_sizes_end_) {
// Ran off end of instruction stream
return VCD_INSTRUCTION_END_OF_DATA;
}
opcode = **instructions_and_sizes_;
if (code_table_data_->inst2[opcode] != VCD_NOOP) {
// This opcode contains two instructions; process the first one now, and
// save a pointer to the second instruction, which should be returned
// by the next call to GetNextInstruction
pending_second_instruction_ = **instructions_and_sizes_;
}
++(*instructions_and_sizes_);
instruction_type = code_table_data_->inst1[opcode];
instruction_size = code_table_data_->size1[opcode];
instruction_mode = code_table_data_->mode1[opcode];
// This do-while loop is necessary in case inst1 == VCD_NOOP for an opcode
// that was actually used in the encoding. That case is unusual, but it
// is not prohibited by the standard.
} while (instruction_type == VCD_NOOP);
if (instruction_size == 0) {
// Parse the size as a Varint in the instruction stream.
switch (*size = VarintBE<int32_t>::Parse(instructions_and_sizes_end_,
instructions_and_sizes_)) {
case RESULT_ERROR:
VCD_ERROR << "Instruction size is not a valid variable-length integer"
<< VCD_ENDL;
return VCD_INSTRUCTION_ERROR;
case RESULT_END_OF_DATA:
UnGetInstruction(); // Rewind to instruction start
return VCD_INSTRUCTION_END_OF_DATA;
default:
break; // Successfully parsed Varint
}
} else {
*size = instruction_size;
}
*mode = instruction_mode;
return static_cast<VCDiffInstructionType>(instruction_type);
}
}; // namespace open_vcdiff
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